Edgecombe County’s Extension Master Gardener Volunteers’ weekly local Q&A column, “Ask A Master Gardener” is intended to engage the county’s residents in solving common problems concerning horticulture, gardening, and pest management through its trained and supervised volunteer staff. The Extension Master Gardener program is an educational program designed to enhance public education in consumer horticulture.
Submit your questions with your email to firstname.lastname@example.org. Or, you can call the local Extension Center at 641-7815 and tell them you have a question for a master gardener. You ask the questions and a local Master Gardener will return your call with a solution to your problem and share it with our readers.
Answers reflect research collected from land grant universities (NCSU or NCA&T) and through a national extension website, www.extension.org.
Q. Ruby K. (in the county) asks Why are my tomatoes wilting and dying in the garden?
A. Tomatoes are susceptible to several wilt diseases caused by soil-borne organisms or environmental conditions. Here’s a link to Clemson University’s extension service site that identifies every known tomato disease. Your Master Gardener Volunteer has singled out three that closely match your problem. http://www.clemson.edu/extension/hgic/pests/plant_pests/veg_fruit/hgic2217.html
Bacterial wilt or Southern bacterial blight is a serious disease caused by Ralstonia solanacearum (formerly Pseudomonas solanacearum). This bacterium survives in the soil for extended periods and enters the roots through wounds made by transplanting, cultivation or insects and through natural wounds where secondary roots emerge. Disease development is favored by high temperatures and high moisture. The bacteria multiply rapidly inside the water-conducting tissue of the plant, filling it with slime. This results in a rapid wilt of the plant, while the leaves stay green. If an infected stem is cut crosswise, it will look brown and tiny drops of yellowish ooze may be visible.
Prevention & Treatment: Control of bacterial wilt of plants grown in infested soil is difficult. Rotation with non-susceptible plants, such as corn, beans and cabbage, for at least three years provides some control. Do not use pepper, eggplant, potato, sunflower or cosmos in this rotation. Remove and destroy all infected plant material. Plant only certified disease-free plants. The cultivar Kewalo is partially resistant to bacterial wilt, but is an uncommon cultivar. Chemical control is not available for this disease.
Fusarium Wilt This is a warm-weather disease caused by the fungus Fusarium oxysporum. The first indication of disease in small plants is a drooping and wilting of lower leaves with a loss of green color followed by wilting and death of the plant. Often leaves on only one side of the stem turn golden yellow at first. The stem of wilted plants shows no soft decay, but when cut lengthwise, the lower stem will have a dark brown discoloration of the water-conducting vessels. The fungus is soil-borne and passes upward from the roots into the water-conducting system of the stem. Blocking of the water-conducting vessels is the main reason for wilting. Invasion occurs through wounds in roots growing through infested soil. Long-distance spread is through seed and transplants.
Prevention & Treatment: Control can be obtained by growing plants in pathogen-free soil, using disease-free transplants and growing only cultivars at least resistant to races 1 and 2 of Fusarium wilt (indicated by FF following the tomato cultivar name). Some newer cultivars are resistant to races 1, 2 and 3, and can be found listed in Table 4. Raising the soil pH to 6.5-7.0 and using nitrate nitrogen (such as in calcium nitrate) rather than ammoniacal nitrogen (as in 5-10-10, 10-10-10, or 34-0-0) will retard disease development. No chemical control is available.
Southern Blight - The fungus Sclerotium rolfsii causes this disease. The first symptom is drooping of leaves suggestive of other wilts. On the stems, a brown, dry rot develops near the soil line. White fungal growth with brown mustard seed-sized sclerotia may be visible. The stem lesion develops rapidly, girdling the stem and resulting in a sudden and permanent wilt of all aboveground parts. Frequently, a white fungal mat covers the lesions. The fungus can also attack fruits where they touch the soil.
The fungus can survive for years in soil and plant debris. It is favored by moist conditions and high temperatures.
Prevention & Treatment: Crop rotation with non-susceptible grass crops and removal of plant debris immediately after harvest will help to control the disease. Do not plant tomatoes after beans, pepper or eggplant. Calcium nitrate may be applied at transplanting.